Method for determining the center of gravity height of a motor vehicle

Abstract

Method for determining the center of gravity height h sp of a motor vehicle, comprising the following procedural steps: A) Determining a reference setup height z ref of the vehicle and at least one height sensor height z FL , z FR , z RL , z RR ; B) Determining a change in body height δ rad of a wheel from a reference installation height assigned to the wheel z ref of the vehicle and at least one height sensor height z FL , z FR , z RL , z RR ; C1) Determining a longitudinal acceleration a x of the vehicle; C2) Determining a pitch angle θ y ; C3) Determining a pitching angular velocity θ y / t; C4) Determining a pitch angle acceleration θ y / t 2 ; and / or D1) Determining a lateral acceleration a y of the vehicle; D2) Determining a roll angle θ x D3) Determining a roll angular velocity θ x / t D4) Determining a roll angle acceleration θ x / t 2 ; and E) Calculating the center of gravity height h sp using the determined parameters A, B, C1, C2, C3, C4 and / or A, B, D1, D2, D3, D4.

Description

[0001] The invention relates to methods for determining a center of gravity height of a motor vehicle according to the independent claim.

[0002] The invention relates to the technical field of methods for operating a vehicle in which the manner of vehicle operation is modified taking the center of gravity into account. For example, due to the transport of objects on the vehicle roof, such as a ski box or a roof rack, the vehicle's center of gravity may change to such an extent that an adjustment of the settings of a vehicle dynamics controller, such as ESP (Electronic Stability Program), becomes necessary because the control unit no longer functions reliably with the original values ​​for the vehicle's center of gravity.

[0003] A method is known from DE 10 2006 002 973 A1, in which an increase in the vehicle's center of gravity caused by a roof load on the vehicle is detected, and the information obtained is taken into account when adjusting the vehicle's handling with a view to preventing the vehicle from tipping over. The determination of the roof load begins when the roof load is started on the vehicle. Depending on the information recorded, a change to the settings of an electronic driving dynamics control system of the vehicle is activated. For this purpose, a switch is operated when a roof rack is installed. If the manual operation is not triggered due to poor installation or if a roof rack that is designed not to trigger the switch is used, the vehicle will retain its normal driving behavior even with an increased roof load (orchanged center of gravity), the original settings are retained, which is particularly disadvantageous with regard to the function of the ESP, which relies on the vehicle's center of gravity.

[0004] Furthermore, DE 10 247 993 B4 discloses a method for determining the center of gravity of a motor vehicle. In this method, the center of gravity is determined based on the roll motion during a predefined "quasi-static" driving situation. For this purpose, the center of gravity of the vehicle is determined from a variable representing the roll motion and a variable representing the lateral acceleration. The problem with this method is that reliable determination of the center of gravity can only be achieved under certain driving conditions. If no or only very slight roll motion occurs, a change in the center of gravity may not be detected at all, for example, if the road is not curved.

[0005] Furthermore, DE 10 2005 062 286 A1, DE 10 2005 048 718 A1, DE 196 15 311 A1 and DE 699 23 465 T2 are known from the prior art.

[0006] It is the object of the present invention to provide a method for determining a center of gravity height of a motor vehicle which overcomes the disadvantages known from the prior art and, in particular, functions reliably and accurately regardless of the driving situation or at least in a variety of driving situations.

[0007] This problem is solved by a method for determining the center of gravity of a motor vehicle according to the independent claim. Advantageous aspects form the subject matter of the respective subclaims.

[0008] The invention comprises a method for determining a center of gravity height h sp of a motor vehicle with the following procedural steps: A) Determine a reference body height z refof the vehicle and at least one height sensor height z FL , e.g. FR , e.g. RL , e.g. RR ; B) Determining a body height change δ rad of a wheel from a reference body height z assigned to the wheel ref of the vehicle and at least one height sensor height z FL , e.g. FR , e.g. RL , e.g. RR ; C1) Determining a longitudinal acceleration a x of the vehicle; C2) Determining a pitch angle θ y ; C3) Determining a pitch angular velocity θ y / t; C4) Determining a pitch angular acceleration θ y / t 2 ; (and / )or D1) Determining a lateral acceleration a y of the vehicle; D2) Determining a roll angle θ x D3) Determining a roll angle velocity θ x / t D4) Determining a roll angle acceleration θ x / t 2; and E) Calculating a center of gravity height h sp using the determined parameters A, B, C1, C2, C3, C4 (and / or A, B, D1, D2, D3, D4.

[0009] In this way, a method for determining a center of gravity height h sp of a motor vehicle is provided, which determines the center of gravity of the motor vehicle using both a variable representing the roll motion and a variable representing the lateral acceleration, as well as a variable representing the pitch motion and a variable representing the longitudinal acceleration. This provides a method for determining the center of gravity that functions reliably and accurately in a variety of driving situations.

[0010] According to a preferred aspect, the center of gravity height h spcalculated using the following equations (where the vehicle longitudinal acceleration and the vehicle lateral acceleration are in the inertial coordinate system): KeffradLfzgmFzgδrad=axhsp+error(θyt2,θyt,θy,h˙sp) for the longitudinal direction with C1, C2, C3, C4; (and / )or KeffradbfzgmFzgδrad=ayhsp+error(θxt2,θxtθx,h˙sp) for the transverse direction with C1, C2, C3, C4; where K effrad = Effective spring rate for the respective spring [N / m], L fzg = wheelbase [m], m Fzg = vehicle mass [kg], b fzg = vehicle track width [m], a x = Vehicle longitudinal acceleration sensor value [ms -2 ] and a y = Vehicle lateral acceleration sensor value [ms -2 ] is.

[0011] This calculation allows to determine the center of gravity height h sptaking into account an error term that represents the current driving state or the rolling movement and / or the pitching movement.

[0012] Preferably, the method further comprises the method step F1) determining a vehicle longitudinal speed V x and / or vehicle longitudinal acceleration V̇ x , where the center of gravity height h sp is calculated using the following equation (non-inertial coordinate system, e.g. with GPS data): KeffradLfzgmFzgδrad=v˙xhsp+error(θyt2,θyt,θy,h˙sp).

[0013] By determining the center of gravity height in this way, the error term can be taken into account and the calculation variant can be compared with other calculation variants and a calculation variant with a low error rate can be identified and selected.

[0014] Another technically preferred aspect provides that the method further comprises the method step F2) determining a vehicle lateral speed Vy and / or vehicle lateral acceleration V̇ y (non-inertial coordinate system). In this way, the center of gravity height can be determined analogously to the longitudinal direction.

[0015] It is also preferred that the method further comprises the method step G) determining a vehicle vertical acceleration a z This allows the determined value for the center of gravity height to be corrected or determined more precisely.

[0016] Another advantageous aspect provides for the method steps H1), with determining a yaw rate ω z and H2) determine a centrifugal acceleration ω z V x , where the center of gravity height h sp is calculated using the following equation (vehicle lateral acceleration / centrifugal acceleration from non-inertial coordinate system) KeffradbfzgmFzgδrad=ωzvxhsp+error(θxt2,θxt,θx,h˙sp)

[0017] Here, too, a further error term results, which is compared with the error term of other calculation methods in order to advantageously determine the vehicle's center of gravity as accurately and reliably as possible.

[0018] Another particularly preferred aspect provides that the method further comprises the method step "I) Determining a damper current VL, VR, HL, HR." The damper current allows for an additional correction.

[0019] Another advantageous aspect provides for method step "J) Determining a door status T." This allows the method to be triggered at a time when the doors are closed and the center of gravity does not change due to passengers boarding and disembarking during vehicle movement.

[0020] It is particularly advantageous if the method further comprises the method step K) determining a degree of road unevenness F. This allows the method to be suspended if the vehicle is traveling on bumpy roads and the detection of the vehicle's center of gravity is inaccurate.

[0021] It is particularly advantageous if the method described above further comprises the following method steps: 1. Providing a control unit in the vehicle; 2. Providing at least one sensor connected to the control unit for determining a vehicle parameter; 3. Start the control unit and initially determine whether a center of gravity height h sp stored; 4. Decision whether 4a) Determination of weight; 4b) Spring rate determination; 4c) Weight determination and spring rate determination are available and in the case: YES: a calculation of various parameters, such as "mass" and "spring rate" is carried out. mFzgk+1=mFzgk+ΔmFzg At: Keffradk+1=Keffradk+ΔKeffrad At mFzgk+1=mFzgk+ΔmFzg && Keffradk+1=Keffradk+ΔKeffrad

[0022] No: the calculation of the center of gravity height h sp as described above.

[0023] In this way, the advantages of determining the center of gravity height can be realized, in particular, on a control unit already present in the vehicle in the form of a method for operating a motor vehicle.

[0024] The center of gravity height h is particularly advantageous. spcompared with a standard value for the center of gravity height h0. This allows, for example, a load, such as a roof load, to be detected at a certain change. Furthermore, it can be determined whether a change in the setting of a vehicle dynamics control system is necessary if a predetermined threshold is exceeded.

[0025] According to another aspect, the center of gravity height h sp compared with a previously stored center of gravity height h to detect an increase or decrease in the center of gravity height Δh sp This allows dynamics in the center of gravity height to be determined, allowing adjustments to be made to the settings of a vehicle dynamics control system.

[0026] Particularly preferred is at least one driving dynamic control system ABS / ESP / Quattro-Sport / EFP due to the determined center of gravity height h sp set.

[0027] The invention is explained in more detail below with reference to the figures. These show: Fig. 1 a block diagram of the process for determining the center of gravity of a motor vehicle; and Fig. 2 a motor vehicle for operation using a method as in connection with Fig. 1 described.

[0028] The Fig. 1 shows a block diagram to illustrate the sequence of the following process steps: A) Determine a reference body height z ref of the vehicle and at least one height sensor height z FL , e.g. FR , e.g. RL , e.g. RR In this process step, the height of the height sensor z FL , e.g. FR , e.g. RL , e.g. RR of (at least) one wheel or (at least) one axle. For example, the reference body height can be determined using a distance sensor (directed toward the road surface). B) Determining a body height change δ rad of a wheel from a reference body height z assigned to the wheel ref of the vehicle and at least one height sensor height z FL , e.g. FR , e.g. RL , e.g. RR . Depending on whether a pitching or rolling movement occurs or the intensity of these movements, the following steps can be carried out: C1) Determining a longitudinal acceleration a x of the vehicle; C2) Determining a pitch angle θ y ; C3) Determining a pitch angular velocity θ y / t; C4) Determining a pitch angular acceleration θ y / t 2 ; (and / )or D1) Determining a lateral acceleration a y of the vehicle; D2) Determining a roll angle θ x D3) Determining a roll angle velocity θ x / t D4) Determining a roll angle acceleration θ x / t 2 ; and E) Calculating a center of gravity height h sp using the determined parameters A, B, C1, C2, C3, C4 and / or A, B, D1, D2, D3, D4.

[0029] In process step E, the center of gravity height h sp calculated using the following equations (inertial coordinate system): KeffradLfzgmFzgδrad=axhsp+error(θyt2,θyt,θy,h˙sp) for the longitudinal direction with C1, C2, C3, C4; (and / )or KeffradbfzgmFzgδrad=ayhsp+error(θxt2,θxt,θx,h˙sp) for the transverse direction with D1, D2, D3, D4; where K effrad = Effective spring rate for the respective spring [N / m] L fzg = Wheelbase [m] m Fzg = vehicle mass [Kg] is b fzg = vehicle track width [m] a x = Vehicle longitudinal acceleration sensor value [ms -2 ] ay = Vehicle lateral acceleration sensor value [ms -2 ].

[0030] The calculation method is selected taking into account the error term, which in turn takes the driving situation into account. For example, D1.1 may be preferred on winding roads, while C1.1 may be more accurate on straight roads.

[0031] Furthermore, the method in the box marked with the dashed lines as optional additionally comprises the method step F1) Determining a vehicle longitudinal speed V x and / or vehicle longitudinal acceleration V̇ x , where the center of gravity height h sp is calculated using the following equation (non-inertial coordinate system) KeffradLfzgmFzgδrad=v˙xhsp+error(θyt2,θyt,θy,h˙sp)

[0032] Alternatively (or additionally), the method may further comprise the method step F2) determining a vehicle lateral speed V yand / or vehicle lateral acceleration V̇ y (non-inertial coordinate system).

[0033] All process steps shown in the dashed box are optional and do not necessarily have to be carried out in the order shown. For example, the process can optionally include process step G) Determining a vehicle's vertical acceleration a z include.

[0034] The method further comprises the method step H1) determining a yaw rate ω z and H2) Determining a centrifugal acceleration ω Z V x , where the center of gravity height h sp is calculated using the following equation (non-inertial coordinate system): KeffradbfzgmFzg=δrad=ωzvxhsp+error(θxt2,θxt,θx,h˙sp)

[0035] This calculation method can be performed based on the adjustment, especially the size (absolute value) of the error term.

[0036] Optionally, the method further comprises the method step I) determining a damper current VL, VR, HL, HR to correct the error.

[0037] Optionally, the method further comprises the method step J) determining a door status T.

[0038] Optionally, the method further comprises the method step K) determining a degree of road unevenness F.

[0039] Optionally, the method further comprises the method step L) checking the error term of equations C1.1, C1.2 and D1.1 and D1.2 and either using the equation with the lower absolute value in the error term or the vehicle center of gravity resulting from this equation or a predetermined driving situation criterion.

[0040] In Fig. 2 shows a vehicle 1 with a roof rack. The vehicle 1 includes a control unit 2 and several sensors 3 connected to the control unit 2 (only one of which is shown as an example) for determining a vehicle parameter.

[0041] It explicitly refers to the procedure which is related to Fig. 1. This procedure can be performed on the control unit as follows: Starting the control unit 2 and initially determining whether a center of gravity height h sp stored; The decision will then be made as to whether a) determination of weight; b) Spring rate determination c) Weight determination and spring rate determination is present and in the event: YES: various parameters such as “mass” and “spring rate” are calculated mFzgk+1=mFzgk+ΔmFzg Keffradk+1=Keffradk+ΔKeffrad KFzgk+1=mFzgk+ΔmFzg && Keffradk+1=Keffradk+ΔKeffrad in the case

[0042] No: the calculation of the center of gravity height h sp as in connection with Fig. 1 described.

[0043] Optionally, the procedure includes that the center of gravity height h sp compared with a standard value for the center of gravity height h0.

[0044] Optionally, the procedure includes that the center of gravity height h sp is compared with a previously stored center of gravity height h0 in order to detect an increase or decrease in the center of gravity height Δh sp to determine.

[0045] Optionally, the procedure includes that at least one driving dynamics control system ABS / ESP / Quattro-Sport / EFP is activated based on the determined center of gravity height h sp is set.

Claims

[1] Method for determining a center of gravity height h sp of a motor vehicle, comprising the following method steps: A) Determine a reference body height z ref of the vehicle and at least one height sensor height z FL , e.g. FR , e.g. RL , e.g. RR ; B) Determining a body height change δ rad of a wheel from a reference body height z assigned to the wheel ref of the vehicle and at least one height sensor height z FL , e.g. FR , e.g. RL , e.g. RR ; C1) Determine a longitudinal acceleration a x of the vehicle; C2) Determining a pitch angle θ y ; C3) Determining a pitch angular velocity θ y / t; C4) Determining a pitch angular acceleration θ y / t 2 ; and / or D1) Determine a lateral acceleration a y of the vehicle; D2) Determining a roll angle θ x D3) Determining a roll angle velocity θ x / t D4) Determining a roll angle acceleration θ x / t 2 ; and E) Calculating a center of gravity height h sp using the determined parameters A, B, C1, C2, C3, C4 and / or A, B, D1, D2, D3, D4. [2] Method according to claim 1, wherein the center of gravity height h sp is calculated using the following equations: KeffradLfzgmFzgδrad=axhsp+error(θyt2,θyt,θy,h˙sp) for the longitudinal direction with C1, C2, C3, C4; and / or KeffradbfzgmFzgδrad=ayhsp+error(θxt2,θxt,θx,h˙sp) for the transverse direction with D1, D2, D3, D4; where K effrad = Effective spring rate for the respective spring [N / m] L fzg = Wheelbase [m] m Fzg = vehicle mass [kg] b fzg = vehicle track width [m] a x = Vehicle longitudinal acceleration sensor value [ms -2 ] a y = Vehicle lateral acceleration sensor value [ms -2 ] is. [3] Method according to claim 1 or 2, further comprising the method step F1) determining a vehicle longitudinal speed V x and / or vehicle longitudinal acceleration V̇ x , where the center of gravity height h sp is calculated using the following equation: KeffradLfzgmFzgδrad=v˙xhsp+error(θyt2,θyt,θy,h˙sp) [4] Method according to claim 1 or 2, further comprising the method step F2) determining a vehicle lateral speed V y and / or vehicle lateral acceleration V̇ y . [5] Method according to one of the preceding claims, further comprising the method step G) determining a vehicle vertical acceleration a z . [6] Method according to one of the preceding claims, further comprising the method step H1) determining a yaw rate ω z and H2) Determining a centrifugal acceleration ω Z V x , where the center of gravity height h sp is calculated using the following equation: KeffradbfzgmFzgδrad=ωzvxhsp+error(θxt2,θxt,θx,h˙sp) [7] Method according to one of the preceding claims, further comprising the method step I) determining a damper current VL, VR, HL, HR. [8] Method according to one of the preceding claims, further comprising the method step J) determining a door status T. [9] Method according to one of the preceding claims, further comprising the method step K) determining a degree of road unevenness F. [10] Method according to one of the preceding claims, further comprising the method step L) either checking the error term of the equations C1.1, C1.2, D1.1 and D1.2 and using the equation with the lower absolute value in the error term or in a predetermined driving situation. [11] Method according to one of the preceding claims, further comprising the method steps:

1. Providing a control unit (2) in the vehicle (1); 2. Providing at least one sensor (3) connected to the control unit (2) for determining a vehicle parameter according to one of the preceding claims; 3. Start the control unit (2) and initially determine whether a center of gravity height h sp stored; 4. Decision whether 4a) Determination of weight; 4b) Spring rate determination; 4c) Weight determination and spring rate determination is present and in case: YES: a calculation of various parameters, such as “mass” and “spring rate” is carried out. If: mFzgk+1=mFzgk+ΔmFzg At: Keffradk+1=Keffradk+ΔKeffrad At KFzgk+1=mFzgk+ΔmFzg && Keffradk+1=Keffradk+ΔKeffrad in case No: the calculation of the center of gravity height h sp according to one of the preceding claims. [12] Method according to one of the preceding claims, wherein the center of gravity height h sp compared with a standard value for the center of gravity height h0. [13] Method according to one of the preceding claims, wherein the center of gravity height h sp is compared with a previously stored center of gravity height h in order to detect an increase or decrease in the center of gravity height Δh sp to determine. [14] Method according to one of the preceding claims, wherein at least one driving dynamics control system ABS / ESP / Quattro-Sport / EFP is activated on the basis of the determined center of gravity height h sp is set.

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